SettingsSettings for this calculationUS
Which kind of figure the plant's reference levels are.
BS 5228-1 and the US Federal Highway Administration's RCNM both publish tables of typical plant noise, at different reference distances; manufacturers declare a sound power level, which is independent of distance. The three are turned into the level at the receptor in different ways, so the basis has to match the figures entered.
The item's level in the form the reference basis above asks for.
From BS 5228-1 Annex C, which tabulates an activity LAeq at its standard reference distance for hundreds of items of plant; from a manufacturer's declared sound power level; or from the FHWA RCNM equipment table, which gives a maximum level at its own reference distance. All three items use the one basis chosen above, and that choice sets the reference distance.
Straight-line distance from the plant to the receptor.
Measured from where the plant works to the point being assessed — usually a window or the facade of the nearest occupied building. For plant that moves about an area, use its average working position, or run the page again for the nearest and farthest positions.
The share of the assessment period the plant is actually working — 0 leaves the item out.
BS 5228-1's on-time and RCNM's usage factor are the same idea: a breaker working half the day contributes half the energy. Set an item to zero to leave it out of the total.
The item's level in the form the reference basis above asks for.
From BS 5228-1 Annex C, which tabulates an activity LAeq at its standard reference distance for hundreds of items of plant; from a manufacturer's declared sound power level; or from the FHWA RCNM equipment table, which gives a maximum level at its own reference distance. All three items use the one basis chosen above, and that choice sets the reference distance.
Straight-line distance from the plant to the receptor.
Measured from where the plant works to the point being assessed — usually a window or the facade of the nearest occupied building. For plant that moves about an area, use its average working position, or run the page again for the nearest and farthest positions.
The share of the assessment period the plant is actually working — 0 leaves the item out.
BS 5228-1's on-time and RCNM's usage factor are the same idea: a breaker working half the day contributes half the energy. Set an item to zero to leave it out of the total.
The item's level in the form the reference basis above asks for.
From BS 5228-1 Annex C, which tabulates an activity LAeq at its standard reference distance for hundreds of items of plant; from a manufacturer's declared sound power level; or from the FHWA RCNM equipment table, which gives a maximum level at its own reference distance. All three items use the one basis chosen above, and that choice sets the reference distance.
Straight-line distance from the plant to the receptor.
Measured from where the plant works to the point being assessed — usually a window or the facade of the nearest occupied building. For plant that moves about an area, use its average working position, or run the page again for the nearest and farthest positions.
The share of the assessment period the plant is actually working — 0 leaves the item out.
BS 5228-1's on-time and RCNM's usage factor are the same idea: a breaker working half the day contributes half the energy. Set an item to zero to leave it out of the total.
Whether a hoarding, bund or building stands between the plant and the receptor.
BS 5228-1 allows about 5 dB where a barrier just breaks the line of sight and about 10 dB where it hides the plant completely. A barrier only helps if it is close to the plant or close to the receptor and has no gaps; a hoarding with an open gate beside a breaker does little.
Predicted level at the receptor, LAeq over the period
70.68 dB(A)
70.7 dB(A) is the predicted LAeq over the period at the receptor from the items entered, over hard ground in neutral weather. Item 1 is most of it: on a logarithmic scale the loudest source decides the total, and moving or screening it changes the result far more than doing the same to the others.
- Plant item 1 at the receptor
- 69.25 dB(A)
- Plant item 2 at the receptor
- 61.79 dB(A)
- Plant item 3 at the receptor
- 62.5 dB(A)
- Plant item 1's share of the total
- 71.89 %
They open the calculator with your figures already in it
Construction Plant Noise at a Neighbour Calculator (BS 5228-1 / FHWA RCNM): 70.68 dB(A) — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- BS 5228-1:2009+A1:2014, Annex F: from an activity LAeq measured at 10 m, the level at distance R over hard ground is LAeq,10m − 20 log10(R ÷ 10), with an on-time correction of 10 log10 of the fraction of the period the plant operates, and levels from several items combined on energy
- ISO 9613-2: geometric divergence from a point source is 20 log10(d) + 11 dB, so a source on hard ground radiating into a hemisphere gives LWA − 20 log10(R) − 8 at R metres
- BS 5228-1, Annex F: a barrier that just interrupts the line of sight between the plant and the receptor reduces the level by about 5 dB, and one that screens the plant completely by about 10 dB
- FHWA Roadway Construction Noise Model (RCNM), FHWA-HEP-05-054: Leq = Lmax at 50 ft − 20 log10(D ÷ 50) + 10 log10(usage factor ÷ 100) − shielding, with the items combined on energy
Inputs used
- Reference Levels Are Given As
- Activity LAeq at 10 m (BS 5228-1 Annex C)
- Plant Item 1 Reference Level (dB(A))
- 80
- Plant Item 1 Distance to the Receptor
- 98 ft
- Plant Item 1 On-Time (%)
- 75
- Plant Item 2 Reference Level (dB(A))
- 78
- Plant Item 2 Distance to the Receptor
- 150 ft
- Plant Item 2 On-Time (%)
- 50
- Plant Item 3 Reference Level (dB(A))
- 84
- Plant Item 3 Distance to the Receptor
- 195 ft
- Plant Item 3 On-Time (%)
- 25
- Screening Between Plant and Receptor
- None — clear line of sight
Intermediate steps
- Plant item 1 at the receptor
- 69.25 dB(A)
- Plant item 2 at the receptor
- 61.79 dB(A)
- Plant item 3 at the receptor
- 62.5 dB(A)
- Plant item 1's share of the total
- 71.89 %
Confidence note: 70.7 dB(A) is the predicted LAeq over the period at the receptor from the items entered, over hard ground in neutral weather. Item 1 is most of it: on a logarithmic scale the loudest source decides the total, and moving or screening it changes the result far more than doing the same to the others.
What this calculation does not cover
- It is a free-field prediction over hard ground, the conservative case. Soft ground, a long grassed or planted stretch in between, reduces the level at larger distances, and a reading taken 1 m (about 3 ft) in front of a building's facade includes a reflection that usually adds about 3 dB.
- Wind direction and temperature gradients change the level at a neighbour by several decibels from day to day; the prediction is for neutral conditions.
- Plant moving along a haul road is a line source, not a point, and BS 5228-1 treats it with a different method; so is plant whose noise is tonal or impulsive, which assessments often penalise.
- It predicts the level; it does not say what is allowed. The limits at a neighbour come from the planning conditions, the local authority, a prior consent or a local noise ordinance.
- Vibration from piling, breaking and compaction is a separate assessment under BS 5228-2 and is not covered here.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-21 · v1.0.0
Regulatory standards & verification citations4
- BS 5228-1:2009+A1:2014, Annex F: from an activity LAeq measured at 10 m, the level at distance R over hard ground is LAeq,10m − 20 log10(R ÷ 10), with an on-time correction of 10 log10 of the fraction of the period the plant operates, and levels from several items combined on energy
- ISO 9613-2: geometric divergence from a point source is 20 log10(d) + 11 dB, so a source on hard ground radiating into a hemisphere gives LWA − 20 log10(R) − 8 at R metres
- BS 5228-1, Annex F: a barrier that just interrupts the line of sight between the plant and the receptor reduces the level by about 5 dB, and one that screens the plant completely by about 10 dB
- FHWA Roadway Construction Noise Model (RCNM), FHWA-HEP-05-054: Leq = Lmax at 50 ft − 20 log10(D ÷ 50) + 10 log10(usage factor ÷ 100) − shielding, with the items combined on energy
Which documents these citations point at
Standards referenced: ISO 9613-2 (International Organization for Standardization, International).
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